1. Field of the Invention
This invention relates to radio frequency communication. More specifically, it relates to tuning of devices to selectively receive desired signals.
2. Brief Description of the Related Art
Consumer demand for wireless connectivity by smart phones, pads and notebook computers (“smart phones”) is exploding, with national demand expected to exceed capacity by 2013. In response, the federal government is expanding the amount of unlicensed spectrum available to consumers. This newly available spectrum and the need for more efficient use of existing spectrum are driving the rapid proliferation of frequency band to which a smart phone must tune.
Existing filter and off-chip resonator technology used to select frequency channels can be tuned only over a limited frequency range. As a result, the number of filters integrated in a smart phone is growing rapidly, increasing the cost, complexity and space burden imposed by the filters. Without a widely tunable filter, the proliferation of filters will adversely impact the economic value of smart phone, degrade consumer acceptance and slow growth of the industry.
In light of the above, we disclose interference based tuning devices and methods for smart phones to isolate radio frequency signals of interest. Tuning by interference employing control of amplitude, phase and group delay enables an ultra-wideband tunable filter that can be tuned rapidly and reliably to any current or anticipated mobile wireless frequency.